EP-A-2 607 636 describes an example of a cam follower for an injection pump.
Classically, a cam follower comprises at least a tappet, a pin and a roller. The pin and the roller are centered on a transverse axis, while the tappet extends along a longitudinal axis. The tappet is formed with two lateral flanges, delimiting an intermediate gap between them and each comprising a cylindrical bore. The roller is positioned in the intermediate gap, between both flanges and bores. The pin is fitted in the two bores, such that the roller is movable in rotation relative to the pin around its axis. The pin may be caulked, in other words plastically deformed, on both opposite ends to create a mechanical connection by press-fit in the tappet bores.
During the roller manufacturing, it is known to grind its lateral faces with two grinding discs. The roller is moved through a gap set between the two discs. The gap has a predetermined width equal to the wished width of the roller. Due to the roughness of the discs and the relative movement between the roller and the discs, such grinding operation makes random traces on the lateral faces of the roller.
When the cam follower is in service, the roller collaborates with a cam synchronized with the internal combustion engine camshaft. The rotation of the camshaft leads to a periodic displacement of a piston of the pump that rests against the tappet, to allow fuel to be delivered. The tappet is movable back and forth along the longitudinal axis, while the roller is movable in rotation around its central axis. The lateral faces of the roller are likely to slide against the lateral flanges of the tappet, with friction therebetween.
In practice, the random traces made by the grinding operation are likely to facilitate oil leakage by centrifugal effect at the interface between the lateral faces of the roller and the lateral flanges of the tappet. Moreover, those random traces are likely to increase the friction at this interface. Thus, the operation of the cam follower may be hampered, which is not satisfactory.